The present invention relates to a non-ablative method and apparatus for making an economical hard disk (platter) for a computer hard disk drive (HDD) using a material machining technique involving filamentation by burst ultrafast laser pulses that is better suited to mass production. The current method of making the platters that store data inside hard disks has been refined so much that it does not allow for further significant improvements without the use of this novel machining technique.
Hard disk drives are data storage devices used for storing and retrieving digital information using rapidly rotating disks (platters) coated with magnetic material. A HDD consists of one or more rigid (“hard”) rapidly rotating disks (“platters”) with magnetic heads arranged on a moving actuator arm to read and write data to the surfaces. HDDs were introduced by IBM in the mid 1950's and are still the dominant secondary storage device for servers and personal computers.
A HDD records data by magnetizing a thin film of ferromagnetic material on a disk. Sequential changes in the direction of magnetization represent binary data bits. The data is read from the disk by detecting the transitions in magnetization. User data is encoded using an encoding scheme, such as run-length limited encoding which determines how the data is represented by the magnetic transitions.
A typical HDD design consists of a spindle that holds flat circular disks, also called platters, which hold the recorded data. In the HDD the hard-drive heads fly and move radially over the surface of the spinning platters to read or write the data. Extreme smoothness, durability, and perfection of finish are required properties of a hard-disk platter. The platters are typically made from a non-magnetic material, usually aluminum alloy, glass, or ceramic that is then coated with a thin magnetic material and a protective overcoat. While the coatings that are applied to the disk give it the data storage properties, the blank has to be perfect in every shape, form and plane before any of these coating processes can occur.
Platters made from a glass substrate have outstanding data storage capacity and higher access speeds than plastic substrates but are more costly to manufacture. Glass is the substrate of preference for HDDs because they achieve a more balanced platter (more even thickness), can withstand more rotational stress, have higher shock resistance and increased reliability, are much smoother than the other substrate materials (important for low fly height) and don't deform as readily under centrifugal loads (better for low fly heights and high TPI). Glass has a coefficient of thermal expansion close to the stainless steel of the motor hub, reducing deformation as the HDD heats up. Glass is stronger than Aluminum for the same thickness so glass platters can be thinner (important for a laptop's low-profile HDD or for high capacity HDDs with multiple platters). Glass is also better for non-operating shock for HDDs that “land” heads on the media, because glass is harder for the heads to dent. Simply stated, glass is the preferred substrate media for HHDs but is quite a bit more expensive than the other HDD substrate medias.
The cost for the glass itself accounts for some of the higher price but the majority of this difference is because of the cost of the additional steps to get the glass blank platter prepared for coating. Utilizing a glass substrate in conjunction with recent discoveries in transparent material machining will result in a simplified fabrication process that will eliminate fabrication steps and fabrication costs, therein rendering glass platters the financially advantageous choice. Henceforth, a faster, economical system for eliminating steps in the fabrication of HDD platters by using a material machining technique involving filamentation by burst ultrafast laser pulses would fulfill a long felt need in the industry. This new invention utilizes and combines known and new technologies in a unique and novel configuration to overcome the aforementioned problems and accomplish this.